This application claims the benefit of Korean Patent Application No. 2000-83768, filed on Dec. 28, 2000 in Korea, which is hereby incorporated by reference as if fully set forth herein.
1. Field of the Invention
The present invention relates to a plasma processing apparatus, and more particularly to a plasma etching apparatus which dry-etches thin films or layers formed on a substrate for a liquid crystal display.
2. Discussion of Related Art
Plasma is an electrically neutral, highly organized gas composed of ions, electrons and neutral particles. The plasma is a phase of matter distinct from solids, liquids, and normal gases. Because plasmas are conductive and respond to electric and magnetic fields and can be efficient sources of radiation, they are usable in numerous applications where such control is needed or when special sources of energy or radiation are required. In recent years, such plasmas are introduced in the areas of plasma technology, such as thin film deposition, display systems (e.g., Plasma Display Panel (PDP)), bulk materials work, plasma-based lighting systems, environmental and health applications and materials synthesis. Among the various areas of plasma technology, plasmas are especially adopted in the field of manufacturing semiconductor devices and liquid crystal display devices, which need large-scale integrated circuits.
A plasma etching apparatus generally etches polymer and metal layers using plasmas generated by the glow discharge at a low temperature, thereby forming the large-scale integrated devices. The plasma etching apparatus widely includes a reaction chamber, a gas feeding member and a voltage supply. The reaction chamber is a sealed container containing processing gases and the gas feeding member introduces reaction gases into the reaction chamber. The voltage supply is connected to electrodes inside the reaction chamber and applies a radio frequency (RF) power to generate plasmas in the reaction chamber. The processing gases from the gas feeding member are converted into the plasmas in the reaction chamber by the electrodes.
FIG. 1 is a schematic sectional view of a conventional plasma etching apparatus. As shown in FIG. 1, the conventional plasma etching apparatus 1 includes a reaction chamber 1a, a radio frequency (RF) power supply 17 and gas-exhaust members 22 and 24. The reaction chamber 1 widely includes a gas inlet 6 through which processing gases are introduced, a plasma diffusing area 2 where the processing gases diffuse, and a reaction area 4 where plasmas are generated from the processing gases and etch an object 14. A diffusion plate 8 having a plurality of holes or slits therein is located inside the plasma diffusing area 2. The diffusion plate 8 diffuses the processing gases introduced from the gas inlet 6, whereby the processing gases are easily spread into the reaction area 4. An upper electrode 10 formed of a metallic material is disposed between the plasma diffusing area 2 and the reaction area 4, and acts as a first electrode to generate an electric field when creating the plasmas. An insulator 12 is adjacent to the upper electrode 10. The upper electrode 10 and the insulator 12 generally have a great number of holes (about ten thousands of holes) therein in order to freely ventilate the processing gases.
Still referring to FIG. 1, an object 14, such as a glass substrate or a semiconductor wafer, is located in the reaction area 4. A lower electrode 18 receiving the RF power from the RF power supply 17 is arranged at the bottom of the reaction area 4. The lower electrode 18 serves as a second electrode when forming the plasmas using the processing gases. In the reaction area 4, the object 14 (e.g., the substrate or semiconductor wafer) is etched by the plasmas generated by the upper and lower electrodes 10 and 18.
The lower electrode 18 is preferably made of a metallic material coated with aluminum, and the object 14 is disposed on the aluminum-coated lower electrode 18. A buffer plate 20 having a plurality of vent holes surrounds the lower electrode 18 at the bottom of the reaction area 4. A shielding member 16 made of a ceramic material is disposed between the lower electrode 18 and the buffer plate 20, and surrounds the lower electrode 18 in order to prevent the lower electrode 18 from being exposed. Accordingly, the buffer plate 20, shielding member 16 and lower electrode 18 are located on the same plane at the bottom of the reaction area 4. Further, the object 14 is mounted on an exposed portion of the lower electrode 18. At the bottom of the reaction chamber 1a, the gas-exhausting members 22 and 24, such as vacuum pumps, are disposed in order to remove the gaseous byproducts from the reaction area 4.
The plasma etch processes performed in the above-mentioned plasma etching apparatus 1 will be explained hereinafter. The object 4 having the polymer or metal layer for plasma etching is loaded on the exposed portion of the lower electrode 18. At this time, the object 4 has substantially the same size as the exposed portion of the lower electrode 18. Thereafter, the processing gases flow into the plasma diffusing area 2 through the gas inlet 6, and then the processing gases are diffused by the diffusion plate 8. The diffused processing gases are then spread into the reaction area 4 through the plurality of holes of the upper electrode 10 and insulator 12.
Thereafter, the RF power supply 17 applies the RF power to the lower electrode 18, such that an electric field is induced between the upper electrode 10 and the lower electrode 18. Therefore, the processing gases in the reaction area 4 are ionized to be the plasmas. The plasmas (e.g., the anions and cations) move toward the lower electrode with a high kinetic energy. The plasmas generated in the reaction area 4 allow for the ability to provide an anisotropic etch which is believed to depend on the bombardment with energetic ions on the surface of the object 14. When etching the object 14, the byproducts from the plasma etching are sucked through a plurality of holes through the buffer plate 20 by the gas-exhausting members 22 and 24, which are below the reaction chamber 1a. Accordingly, the layers on the object 14 are patterned by the above-mentioned plasma etching processes.
FIG. 2 is a top plan view of the buffer plate 20 surrounding the shielding member 16 and lower electrode 18. As shown in FIG. 2, the buffer plate 20 includes a plurality of holes 21 therein though which the gaseous byproducts and the residual plasma etchant are removed. Further in FIG. 2, the gas-exhausting members 22 and 24 (e.g., the vacuum pumps) sucking the gaseous byproducts and the residual plasma etchant are located below the reaction chamber 1a of FIG. 1 in areas corresponding to areas xe2x80x9cAxe2x80x9d of FIG. 2. When the gas-exhausting members 22 and 24 are operated, the gaseous byproducts and the residual plasma etchant are sucked by these gas-exhausting members 22 and 24 through the plurality of vent holes 21. However, since the gas-exhausting members 22 and 24 are located in the areas xe2x80x9cAxe2x80x9d, the gaseous byproducts and the residual plasma etchant converge in these areas xe2x80x9cAxe2x80x9d.
In other words, when exhausting the gaseous byproducts and the residual etchant through the plurality of vent holes 21 of the buffer plate 20, suction power is relatively larger in the areas xe2x80x9cAxe2x80x9d than the other area of the buffer plate 20 because the gas-exhausting members 22 and 24 are arranged under the areas xe2x80x9cAxe2x80x9d. Therefore, the density of the byproducts and etchant increases in the areas xe2x80x9cAxe2x80x9d, and then a convergence of the byproducts and etchant occurs in the areas xe2x80x9cAxe2x80x9d. Thus, the convergence of the gaseous byproducts and residual plasma etchant brings about the irregular etch of the object 14 (in FIG. 1) and additionally causes arcing in areas xe2x80x9cBxe2x80x9d of the lower electrode 18.
The arcing phenomenon occurring in the lower electrode 18 will be explained referring to FIGS. 1 and 2. In FIGS. 1 and 2, the buffer plate 20 having the plurality of vent holes 21 is located at the bottom of the reaction area 4. Additionally, the lower electrode 18 surrounded and protected by the shielding member 16 is located at the center of the buffer plate 20. The object 14 is put and fixed on the exposed portion of the lower electrode 18. However, a gap occurs and exists between the object 14 and the shielding member 16 because of the surface irregularity of the object 14 and shielding member 16. This gap is large enough for the plasmas to pass through. Accordingly, since the gaseous byproducts and residual etchant converge in the areas xe2x80x9cAxe2x80x9d, the plasmas strongly strike the lower electrode 18 through the gap in the areas xe2x80x9cBxe2x80x9d of FIG. 2, thereby causing the arcing. Due to the strong and continuous strike of the plasmas, aluminum film coating the lower electrode 18 comes apart from the lower electrode and the lower electrode 18 is exposed in the areas xe2x80x9cBxe2x80x9d of FIG. 2. This arcing phenomenon shortens the life span of the lower electrode 18, and thus the lower electrode 18 should be exchanged after the plasma etching processes. Namely, the convergence of the gaseous byproducts and residual plasma etchant causes the arcing in the lower electrode and then shortens the electrode""s life. Additionally, the convergence of the gaseous byproducts and residual plasma etchant causes the irregular etch of the object, thereby decreasing the stability of the electronic devices that have been etched by this plasma etching process.
Accordingly, the present invention is directed to a plasma etching apparatus that substantially overcomes one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a plasma etching apparatus that prevents convergence of plasmas and gaseous byproducts.
Another advantage of the present invention is to provide a plasma etching apparatus that has an improved etching efficiency and conducts uniform plasma etch.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to achieve the above advantages, a plasma etching apparatus includes a reaction chamber having a diffusion area and a reaction area; an upper electrode disposed in the top of the reaction area; a lower electrode spaced apart from the upper electrode and arranged at the bottom of the reaction area; a RF power supply applying RF power to the upper and lower electrodes so as to form the plasmas between the upper and lower electrodes; a gas inlet applying processing gases to the diffusion area; gas-exhausting members sucking the residual plasmas and byproducts of the plasma etch; a buffer plate surrounding the lower electrode at the bottom of the reaction chamber and having a plurality of vent holes and vent hole protectors; and a shielding member between the lower electrode and the buffer plate, the shielding plate protecting the lower electrode from the plasmas; wherein the buffer plate is divided into a first portion, a second portion and a third portion; wherein the first portion has a size defined by multiplying a length of the shielding member by a distance between the top edge of the shielding member and the top edge of the buffer plate; wherein the second portion has a size defined by multiplying a length of the shielding member by a distance between the bottom edge of the shielding member and the bottom edge of the buffer plate; wherein the plurality of vent holes are arranged in the third portion of the buffer plate; wherein the vent hole protectors are arranged in the first and second positions; and wherein the each vent hole protector corresponds to each gas-exhausting member.
In the aforementioned plasma etching apparatus, the vent hole protectors occupy about 50% space of the first and second portions of the buffer plate, respectively. The plasma etching apparatus further comprises a diffusion plate in the diffusion area, whereby the diffusion plate diffuses the processing gases that flow from the gas inlet.
The aforementioned plasma etching apparatus further comprises an insulator that is arranged adjacent to the upper electrode and has a plurality of holes to ventilate the processing gases. The upper electrode also includes a plurality of holes to ventilate the processing gases. The shielding member is made of a ceramic material.
The first portion of the buffer plate has substantially the same size as the second portion of the buffer plate. Each gas-exhausting member is a vacuum pump.
The vent hole protectors are formed when forming the buffer plate. Alternatively, the vent hole protectors can be made by way of attaching additional plates upon the first and second portions of the buffer plate. Here, the additional plates are an insulating material and has a enough thickness not to affect the plasma etching process.
It is to be understood that both the foregoing description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.